Authentication Bypass Affecting traefik-2 package, versions *


Severity

Recommended
0.0
critical
0
10

Snyk's Security Team recommends NVD's CVSS assessment. Learn more

Threat Intelligence

EPSS
0.06% (19th percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-MINIMOSLATEST-TRAEFIK2-16298317
  • published26 Apr 2026
  • disclosed30 Apr 2026

Introduced: 26 Apr 2026

NewCVE-2026-39858  (opens in a new tab)
CWE-290  (opens in a new tab)
CWE-306  (opens in a new tab)

How to fix?

There is no fixed version for Minimos:latest traefik-2.

NVD Description

Note: Versions mentioned in the description apply only to the upstream traefik-2 package and not the traefik-2 package as distributed by Minimos. See How to fix? for Minimos:latest relevant fixed versions and status.

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a high severity authentication bypass vulnerability in Traefik's ForwardAuth and snippet-based authentication middleware. Traefik's forwarded-header sanitization logic targets only canonical header names (e.g., X-Forwarded-Proto) and does not strip or normalize alias variants that use underscores instead of dashes (e.g., X_Forwarded_Proto). These unsanitized alias headers are forwarded intact to the authentication backend. When the backend normalizes underscore and dash header forms equivalently, an attacker can inject spoofed trust context — such as a trusted scheme or host — through the alias headers and bypass authentication on protected routes without valid credentials. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.

CVSS Base Scores

version 3.1